Modular electrical ground bushing



Aug. 22, 1967 w. H. CREEDON 3,337,333

- MODULAR ELECTRICAL GROUND BUSHING Filed Sept. 4, 1964 ATTORNEYS United States Patent Pennsylvania Filed Sept. 4, 1964, Ser. No. 394,461 1 Claim. (Cl. 339-14) This invention relates to a modular electrical ground bushing, and has as its objective the provision of a construction heretofore unknown.

It is known to provide a connector comprising a metallic plate having spaced openings therein. Insulating bushings of a somewhat compressible plastic material are seated in the openings in the metallic plate, and then a terminal is slipped or forced into the seated bushings.

However, it is sometimes desirable that at least certain of the terminals be grounded to the plate. Since the bushing is of a non-conductive material, it has been the prior practice to provide a specific connection between the terminal and the plate. This has been accomplished in several ways, each of which necessitated special steps which add yet another cost to the operation.

One such technique involved the use of a terminal having an enlarged portion on its shank so that the terminal could be directly received in the plate with the bushing being dispensed with. Another technique involved providing a common ground by means of special etched circuitry on a module card or bus wiring of the back panel.

However, the techniques heretofore used not only increased the manufacturing and assembly costs but also had a tendency to lower the speed of assembly and were quite inflexible since the modifications themselves involved a departure from the construction or assembly of the majority of terminals in the plates.

It is therefore an object of the present invention to provide a modular electrical ground bushing for use in a plate connector which does not appreciably increase the cost of manufacturing or assembly and does not essentially detract from the speed of assembly, but instead can be handled in essentially the same Way as the insulating bushings are handled.

Yet another object of the present invention is to dispense with the special precautions and techniques presently utilized and to replace them with a ground bushing of modular construction which overcomes the shortcomings of the prior devices.

The foregoing as well as other objects of the invention are achieved by subjecting the usual plastic insulating bushings to a special metallizing process, but other metallic coating processes are contemplated by the present invention. A metallizing process well known to those skilled in the art is employed to provide the plastic insulating bushing with a thin conductive metallic coating. The coated insulator bushing may then be electro-plated with copper and then electro-plated with gold. Because the bushing with the metallic coating is essentially of the same configuration as an uncoated bushing, it can be handled by the very same assembly machinery. There is no need for any special manufacturing or assembly techniques except for the metallic coatings steps heretofore outlined which can be carried out on a mass basis. The speed of assembly of the metallic coated bushing into the plate and the insertion of the terminal should be identical with the uncoated bushing.

Other objects and many attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a perspective exploded view of a plate connector showing three insulator bushings connected in gang and a conductive bushing of the present invention seated in the plate with a terminal being seated in the conductive bushing and the plate, and another terminal being shown about to be positioned in one of the insulating bushings after they have been seated in the plate; and

FIG. 2 is an enlarged fragmentary sectional view taken along the lines 22 of FIG. 1.

Referring now to the various figures of the drawing wherein like reference characters refer to like parts, there is shown generally at 10 in FIG. 1 a connector member which includes a modular electrical ground bushing of the present invention.

The connector member 10, as shown in FIG. 1, basically is comprised of metallic plate 12 having openings 14 formed therein which are adapted each respectively to receive one of the insulating bushings 16 or the conductive ground bushing 1d of the present invention.

As shown in FIG. 1, the insulating bushings 16 may be coupled together in gang in the molding thereof so that each of the bushings 16 is secured together in unitary form by virtue of the provision of webbing 2% which joins the respective insulating bushings together.

As previously discussed, the insulating bushings 16 function to hold a terminal securely within metal plate 12, and also to insulate the respective terminals from each other. In order to assemble the connector 11 it is the practice to position the insulating bushings in the openings 14 in the plate 12 and then to slip or force the terminal 22 within the bore 24 of the insulating bushing until the head of the terminal has been seated against the insulating bushing in a manner similar to that shown in FIG. 2.

While there are many varieties of terminals that are usable with the present invention, an example of a terminal 22 is shown in FIG. 1 and is basically comprised of a head section 26 and a tail section 28. The head section 26 includes bifurcated wiping fingers 30 which have free ends that are flared outwardly in tips 32 to facilitate the entry of a mating member or a printed circuit board. The blades 30 also taper outwardly and backwardly as they approach the tail section and then terminate in a shoulder 34. The tail section is elongated and has a generally square cross-section in order to be usable with automatic wire wrapping machinery.

Wherever it is desirable to ground a given terminal 22 to the plate 12, the modular electrical ground bushing 18 of the present invention is utilized. The modular ground bushing 18 is of a construction and configuration generally the same as the insulating bushings 16 with one important difference. This is that the ground bushing 18 has been completely covered, both outside and within the surfaces of its bore, with a conductive layer 36. This is shown in FIG. 2 wherein the conductive coating 36 is shown to extend not only upon the exterior portions of the ground bushing 18, but also within a bore 24. Said conductive coating may be applied by techniques well known to the art. First, a metallizing process is employed to provide the bushing with a thin metal coating. Then copper and gold deposits may be electroplated thereon.

The assembly technique utilizing the ground bushing is identical to the technique used in seating the insulating bushings 16 and terminals 22. Hence, the ground bushing 18 is positioned in a desired opening 14 of the plate 12. The tail 28 of the terminal 22 is then inserted in the bore 24 of the ground bushing 18 so that it will be tightly held therein as shown in FIG. 2. This is accomplished by appropriate selection of the dimensions of the cross-section of the terminal tail 28, the bushing bore 24 and the openings 14in the plate 12.

FIG. 2 illustrates that the terminal 22 is thereby automatically grounded to the plate 12 since there is a continuous conductive path from the tail 28 through the conductive coating 36 to the plate 12 by virtue of the fact that the conductive coating 36 completely covers the interior and exterior of the ground bushing 18 and therefore extends from the bore 24 outwardly to the point where there is physical contact between the plate 12 and the coating 36.

By virtue of the foregoing, there is no need to carry out special steps in order that certain of the terminals secured within the plate 12 may be grounded. All that is necessary is to insert a ground bushing 18 in accordance with the present invention in place of an inserted bushing 16. Other than this, the assembly process is identical and the desired terminals 22 will be automatically grounded.

Obviously many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that Within the scope of the appended claim, the invention may be practiced otherwise than as specifically described.

What is claimed as the invention is:

An electrical connector assembly comprising:

(a) a metallic plate provided with a plurality of holes;

(b) insulated bushings of somewhat compressible material pressed into certain of said holes and retained therein by the compressible nature of said material;

(c) each insulated bushing having a central bore;

(d) a conductive contact retained in the bore of each of said insulated bushings whereby the last mentioned contact is attached to said plate but insulated therefrom;

(e) at least one ground bushing having essentially the same configuration as said insulated bushings including a central bore;

(f) said ground bushingrcomprising a body of insulating material that is somewhat compressible, and a continuous conductive metallic coating on the outer surface of said body including that surface that defines the central bore in the body;

(g) said ground bushing being pressed into a hole in said plate and retained therein by the compressible nature of the material of the body so that the metallic coating on the outer surface thereof electrically engages said plate; and

(h) a contact retained in the bore of said ground bushing so that the last mentioned contact electrically engages the metallic coating on the surface of said body that defines the central bore therein whereby the continuous nature of the metallic coating on the body effects an electrical connection between the contact in the ground bushing and the plate.

References Cited UNITED STATES PATENTS 2,079,784 5/ 1937 Williams.

2,163,412 6/1939 Schneider 339-143 2,359,436 10/1944 Mascuch 339l43 X 2,931,006 3/1960 Klumpp 339-126 X 2,995,617 8/1961 Maximolf et a1. 3392.21 X 3,105,729 10/1963 Rosenthal et al 339-18 MARVIN A. CHAMPION, Primary Examiner.

PATRICK A. CLIFFORD, Examiner. 

